This invention provides a simple and practical method to greatly reduce the size and weight of a single-acting two piston Stirling engine without at the same time increasing its complexity or decreasing its mechanical efficiency.
It is generally agreed that the single-acting two piston Stirling engine is one of the most desirable forms of Stirling for small power applications, having demonstrated both simplicity and good performance. Such engines may be designed in a variety of forms; for example, cylinders may be in a V, in-line, or horizontally opposed arrangement.
One of the most desirable arrangements is the yoke drive described by Ross in U.S. Pat. No. 4,138,897. In this design the lower apex of a triangular yoke is attached to a single-throw crankshaft located beneath twin parallel cylinders. The upper portion of the yoke is constrained by a rocking lever. The upper apexes of the yoke are attached by connecting rods to the respective pistons. Practically all of the side loads encountered in this mechanism are absorbed by the rocking lever bearings. The pistons themselves see very low side loads, and therefore they may be run without liquid lubrication, yet still give long life with low friction losses. The ability to run well without liquid lubrication is an important advantage in a Stirling engine.
Yoke drive Stirling engines have in fact demonstrated excellent mechanical efficiency, and they are relatively simple and inexpensive. Their overall size and weight are comparable to two piston engines of other configurations for a given pressure level and power.
The aim of this invention is to disclose a new form of yoke-based crankdrive mechanism for the two-piston Stirling which offers a very considerable reduction of size and weight in a given engine and yet retains all the known advantages of the previous yoke drive mechanism.
Other aims, features, and advantages will be apparent in the description, below.